An X-ray crystallographic investigation of the structures of pyrazine adducts of diphenyltin dichloride and dimethyltin dichloride

Abstract

Reaction of SnPh2Cl2 with pyrazine (pyz) leads exclusively to the formation of an adduct having the bulk composition SnPh2Cl2·0.75pyz. It has a structure composed of layers in which zig-zag polymeric chains, (SnPh2Cl2·pyz)n, with six-co-ordinate tin, alternate with layers containing non-interacting molecules of (SnPh2Cl2)2·pyz, with five-co-ordinate tin. The Sn–N bond lengths are abnormally long; each tin atom tin atom in the polymeric chains has Sn–N bond lengths of 2.961(10) and 2.783(10)Å, and the Sn–N bond length in (SnPh2Cl2)2·pyz is 2.683(11)Å. Mössbauer spectroscopy does not identify the presence of the two tin sites in the solid whereas 119Sn n.m.r. does. X-Ray crystallographic details are: space group Pbam(orthorhombic), a= 14.935(2), b= 13.409(3), c= 14.959(3)Å, Z= 8(Sn), R= 0.047 (R′= 0.056) for 1 478 observed reflections with I > 3σ(I). Reaction of SnMe2Cl2 with pyrazine leads exclusively to formation of the adduct (SnMe2Cl2)2·pyz; the distannoxane (SnMe2Cl)2O is also formed if solutions are not protected from the atmosphere. The adduct has a chain polymeric structure with six-co-ordinate tin atoms alternatively linked by chloride ions and pyrazine molecules. The Sn–N bond length [2.746(6)Å] is abnormally long. The polymeric chains pack into well defined planes, with chains in alternate planes propagating in orthogonal directions. Crystallographic details are: space group P21/n(monoclinic), a= 6.855(1), b= 10.344(2), c= 12.014(3)Å, β= 92.590(7)°, Z= 2, R= 0.03 (R′= 0.033) for 727 observed reflections with I > 3σ(I).